The purpose of this proposal is to establish the feasibility for applying a new and noninvasive method to the development of a practical instrument for sensitive and quantitative detection of microembolic involvement in human lungs. Because present methods for detection of pulmonary emboli utilize imaging techniques, the size of emboli detectable by these methods are limited by the inherent spacial resolution of x-ray and gamma cameras. Microemboli (obstruction of the microcirculation) are therefore too small to be detected by standard methods. Since microemboli are not detectable, there is no direct evidence that microembolic involvement is of clinical significance. However, microembolic involvement has been shown to be a cause in Adult Respiratory Distress Syndrome (ARDS), a disease having a high mortality (over 50%) in humans. Microembolic involvement in other trauma associated conditions, including surgery, is also speculative. Phase I would address validation of the principle of the new method in experimental animals. The economic goal of Phase II would be to test the likelihood of microembolic detection becoming standard medical practice. Accomplishment of this goal involves a combination of technical development and scientific studies. Given a successful Phase I, Phase II would 1) develop a practical instrument for human studies, and 2) perform clinical research studies designed to verify the speculations of microembolic involvement in ARDS and other trauma associated conditions.